As shown in FIG. 1, a prior art liquid pump is capable of drawing liquid up by suction created by a manually-operated piston fitted into the cylinder. Such a prior art liquid pump as described above is rather primitive in construction and is therefore rather inefficient.
Another prior art liquid pump is shown in FIG. 2 and is provided with a pressure ball capable of creating a suction force to draw liquid up via a one-way movable gate. Such a conventional liquid pump as described above is limited in design n that it is not suitable for use in drawing up a heavy liquid having a high viscosity.